The honey bee, Apis mellifera, is the third most important animal for agricultural production following swine and cattle. Honey bees required for effective pollination of crops are therefore critical to world agriculture. Industrial production of fruits, vegetables and oleiferous fruits is in particular dependent on honey bees. Against this background the massive collapse of honeybee colonies is threatening worldwide agriculture, in particular in the US and Europe.
The honey bee health is threatened by many factors such as diseases, pesticides or malnutrition in areas of monoculture. Among all the factors affecting the bees, the ectoparasitic mite Varroa destructor is considered to be the main threat to bee health Varroa destructor is an external parasitic mite that attacks the honey bees Apis cerana and Apis mellifera. The disease caused by the mites is called varroosis. Varroa mites parasitize pupae and adult bees and reproduce in the pupal brood cells. The mites use specialized mouthparts to puncture the cuticle and feed on the bees' hemolymph which weakens the bees. The injured bees are also more prone to infections. Varroa mites are moreover assumed to be vectors for a number of honey bee pathogens, including deformed wing virus (DWV), Kashmir bee virus (KBV), acute bee paralysis virus (ABPV) and black queen cell virus (BQCV).
A significant mite infestation will lead to the death of a honey bee colony, usually in late summer or during overwintering. The Varroa mite is the parasite with the most pronounced economic impact on the beekeeping industry and may be one of the core factors for honey bee colony losses including CCD.
Varroa mites have been treated chemically with commercially available miticides, synthetic chemicals such as Fluvalinate and Coumaphos, or naturally occurring chemicals such as formic acid, oxalic acids, lactic acid, mineral oils and others. Non-chemical treatment approaches include the so-called perforated bottom board method, drone brood removal, heat treatments, comb trapping method and others. Recently RNA interference to knock down genes in the Varroa mite have been advocated, see for example WO 2011/045796.
There is nevertheless a continuing need for other treatment options against infestation of colonies of honeybees with Varroa destructor. 